The present invention relates to a compressor including an electric element, and a compression element driven by the electric element in a container, its manufacturing method, a defroster of a refrigerant circuit, and a refrigeration unit.
In a rotary compressor of such a conventional type, especially in a rotary compressor of an internal intermediate pressure multistage compression type, refrigerant gas is supplied through a refrigerant introduction tube and a suction passage, and sucked from a suction port of a first rotary compression element into a low pressure chamber side of a cylinder (first cylinder). The refrigerant gas is then compressed by operations of a roller and a vane engaged with an eccentric part of a rotary shaft to become intermediate pressure, and discharged from a high pressure chamber side of the cylinder through a discharge port and a discharge muffler chamber into a hermetically sealed container. Then, the refrigerant gas of the intermediate presser in the hermetically sealed container is sucked from a suction port of a second rotary compression element into a low pressure chamber side of a cylinder (second cylinder). The refrigerant gas is then subjected to second stage compression by operations of a roller and a vane engaged with an eccentric part of a rotary shaft to become one of a high temperature and high pressure. Then, it is supplied from the high pressure chamber through the discharge port, the discharge passage and the discharge muffler chamber, and discharged from a refrigerant discharge tube to the refrigerant circuit. The refrigerant gas then flows into a radiator constituting the refrigerant circuit with the rotary compressor. After heat radiation, it is squeezed by an expansion valve, heat-absorbed by an evaporator, and sucked into the first rotary compression element. This cycle is repeated.
The eccentric parts of the rotary shafts are provided to have a phase difference of 180°, and connected to each other by a connecting portion.
If a refrigerant having a large high and low pressure difference, for example carbon dioxide (CO2) as an example of carbon dioxide gas, is used for the rotary compressor, discharge refrigerant pressure reaches 12 MPaG at the second rotary compression element, in which pressure becomes high. On the other hand, it reaches 8 MPaG (intermediate pressure) at the first rotary compression element of a low stage side. This becomes pressure in the hermetically sealed container. Suction pressure of the first rotary compression element is about 4 MPaG.
The vane attached to such a rotary compressor is inserted in a groove provided in a radial direction of the cylinder so as to be freely moved in the radial direction of the cylinder. A spring hole (housing portion) opened to the outside of the cylinder is provided in a rear side of the vane (hermetically sealed container side), a coil spring (spring member) for always pressing the vane is inserted into the spring hole, an O ring is inserted into the spring hole from the opening outside the cylinder, and then sealed by a plug (pulling-out stopper) to prevent jumping-out of the spring.
In this case, eccentric rotation of the roller applies a force of extruding the plug from the spring hole to the outside. Especially, in the rotary compressor of the internal intermediate pressure type, since pressure in the hermetically sealed container becomes lower than that in the cylinder of the second rotary compression element, the plug is also extruded by a pressure difference between inside and outside of the cylinder. Thus, in the conventional case, the plug was pressed into the spring hole to be fixed to the cylinder. However, such pressure insertion deformed the cylinder to expand, forming a gap between it and a support member (bearing) for sealing the opening surface of the cylinder. Consequently, it was impossible to secure sealing in the cylinder, reducing performance.
In the rotary compressor of the internal intermediate pressure multistage compression type, since pressure (high pressure) in the cylinder of the second rotary compression element was higher than pressure (intermediate pressure) in the hermetically sealed container as an oil reservoir on a bottom part, it was extremely difficult to supply oil from an oil hole of the rotary shaft into the cylinder by using a pressure difference. Consequently, lubrication was carried out only by oil blended in the sucked refrigerant, causing a shortage of oil supply.
In the rotary compressor of the internal intermediate multistage compression type, the opening surface of the cylinder constituting the second rotary compression element is sealed by the support member, and the discharge muffler chamber is installed in this support member. FIG. 20 shows in section a support member 291 according to a conventional art. A bearing 291A of a rotary shaft is erected on a center of the support member 291, and a bush 292 is attached in the bearing 291A. A discharge muffler chamber 293 is concaved in the support member 291 outside the bearing 291A, and the discharge muffler chamber 293 is sealed by a cover 294. The cover 294 has a peripheral part fixed on the support member 291 by a plurality of bolts.
Here, because of higher pressure in the discharge muffler chamber 293 of the second rotary compression element than intermediate pressure in the hermetically sealed container, sealing by the cover 294 is an important problem. A gasket 296 is accordingly held between the cover 294 and the support member 291, but sealing is deteriorated because the center bearing 291A side is away from the bolt. Thus, in the conventional case, a sealing surface 291B having a step was formed on a base of the bearing 291A, the gasket 296 was also held for sealing at this sealing surface 291B, a C ring 297 was attached to the bearing 291A, and an edge of the bearing 291A side of the cover 294 was pressed to the support member 291 side.
However, in the above-described conventional structure, the formation of the sealing surface reduced a capacity of the discharge muffler chamber, and necessitated the attaching of the C ring. Consequently, both processing and component costs were increased.
With regard to strength of the cover, if thin, the cover was deformed outside by the pressure difference between the discharge muffler chamber and the hermetically sealed chamber, causing gas leakage. Conversely, if too thick, it was impossible to secure an insulation distance from the electric element, causing an increase in a height dimension of the entire compressor.
The discharge pressure of the second rotary compression element becomes extremely high as described above. In the conventional case, however, each cylinder was fastened to the support member having the bearing by bolts arranged concentric circularly around the bearing. Consequently, there was a possibility of gas leakage from the cylinder.
When the high and low pressure difference is high as described above, if the connecting portion of the rotary shaft has a circular sectional shape coaxial to the rotary shaft, a sectional area to be physically secured is small, and the rotary shaft is easily deformed elastically. Thus, in the conventional case, in order to increase strength, a section of the connecting portion was formed in a rugby ball shape, in which a thickness in a direction orthogonal to the eccentric direction was larger than that in the eccentric direction of both eccentric portions. However, the number of processing steps was increased in a cutting process of the rotary shaft, deteriorating productivity.
In the compressor of the hermetically sealed type, the hermetically sealed container must be subjected to airtightness testing in a completion test of a manufacturing process. Pressure for this test is set to about 4 MPa in a normal compressor. However, if CO2 is used as a refrigerant as described before, since pressure (intermediate pressure in the above-described case) of the hermetically sealed container becomes extremely high, test pressure of about 10 MPa as a design upper limit of intermediate pressure is required. Consequently, it was difficult to easily connect a compressed air generator for applying the test pressure into the hermetically sealed container to the compressor.
To carry out gas-liquid separation of the refrigerant gas sucked into the first rotary compression element, an accumulator is attached to the hermetically sealed container. This accumulator is attached to a bracket welded to a side face of the hermetically sealed container by welding or a band, and held along the outside of the hermetically sealed container. However, if there is a need to increase a capacity of the accumulator or the like, the accumulator and a pile such as a refrigerant introduction tube may interfere with each other.
Therefore, conventionally, a shape of the bracket itself was changed to be separated from the pipe, or the holding position of the accumulator was changed to separate the accumulator itself from the pipe. In the former case, since the bracket was hooked on a hanger of a production device during painting of the hermetically sealed container, the hanger for painting had to be changed. In the latter case, since the accumulator was held away from its center (or position of center of gravity), vibration of the accumulator itself was increased, resulting in larger noise.
When the refrigerant gas of intermediate pressure discharged into the hermetically sealed container is sucked through another refrigerant introduction tube located outside the hermetically sealed container into the second rotary compression element, the refrigerant introduction tubes of the first and second rotary compression elements are connected to the hermetically sealed container in positions adjacent to each other.
Thus, wiring becomes difficult because of mutual interference between both refrigerant introduction tubes. Especially, since the accumulator was normally connected to the refrigerant introduction tube to the first rotary compression element, and this accumulator was arranged above the connecting position of each refrigerant introduction tube, interference easily occurred between both refrigerant introduction tubes, and it was difficult to lower the position of the accumulator.
In such a rotary compressor, a terminal for feeding power to the electric element is attached to an end cap of the hermetically sealed container. FIG. 23 shows in section a terminal 299 of the conventional rotary compressor. The terminal 299 was fixed by welding to an upper surface of an end cap 298 exhibiting an asymmetrical sectional shape at a center as shown.
In the end cap 298, by receiving an effect of high internal pressure, its welded part with the terminal 299 is deformed in a direction of being swelled outside. In an upper part of FIG. 23, a result of actually measuring a deformation amount of the end cap 298 is shown by region by region. In the drawing, a deformation amount of a region indicated by Z4 is 0.2 μm. a deformation amount of a region indicated by Z5 is larger, i.e., 0.5 μm, and a deformation amount of a region indicated by Z6 is increased further more to a maximum 0.9 μm.
Thus, because of the largest deformation amount of the terminal 299, cracks or welding peeling-off occurred in the welded part between the terminal 299 and the end cap 298, consequently causing a reduction in pressure resistance performance.
FIG. 25 shows in section a terminal 300 of another rotary compressor. The terminal 300 includes a circular glass portion 302 provided with an electric terminal 307, and a metal attaching portion 303 formed around it. This attaching portion 303 was welded to a peripheral edge of an attaching hole 306 formed in a hermetically sealed container 304.
In this case, when the attaching portion 303 of the terminal 300 was too thin, strength (pressure resistance performance) against high pressure of refrigerant gas in the hermetically sealed container became insufficient, causing a failure such as cracks in the attaching portion 303. On the other hand, when too thick, a great amount of heat was necessary for welding the hermetically sealed container 304, causing damage to the glass portion 302 by the heat. Consequently, there was a danger of gas leakage or destruction.
An opening surface of a cylinder of such a rotary compressor is sealed by a support member constituting a discharge muffler chamber inside and, on a center of the support member, a bearing of a rotary shaft of an electric element is provided. Then, by providing a carbon bush capable of maintaining good sliding performance even in insufficient oil supply, and having high wear resistance performance even with respect to a high PV value (load applied per unit area) during a high load between the bearing and the rotary shaft, durability of the rotary compressor can be greatly improved. However, such a carbon bush was disadvantageous because a price was high, increasing competent costs.
The above-described refrigerant introduction and discharge tubes are connected to a cylindrical sleeve welded to a bent surface of the hermetically sealed container. Conventionally, however, a fixture was used to obtain perpendicularity of the sleeve with respect to an inner diameter of the hermetically sealed container. Consequently, assembling workability was deteriorated, lowering accuracy of perpendicularity.
For the rotary compression element to become high in pressure, a thin cylinder is used. Thus, since a suction passage or a discharge passage cannot be formed within the thickness range of the cylinder, a suction passage and a discharge passage are formed on the support member side sealing the opening surface of the cylinder and having a bearing and, in the cylinder, the suction and discharge ports for communicating the suction passage and the discharge passage with the inside of the cylinder are obliquely formed.
FIGS. 31 and 32 show a conventional processing method of such suction and discharge ports. In each drawing, a reference numeral 311 denotes a cylinder constituting a rotary compression element, 312 a suction port obliquely formed in the cylinder 311, and 313 a discharge port. In the case of forming the suction port 312, an end mill ML1 having a flat tip is set obliquely to the cylinder 311, i.e., in a direction perpendicular to a slope of the suction port 312, and moved in an inclining direction of the suction port 312 as indicated by an arrow in FIG. 31, thereby forming a groove inclined with respect to the cylinder 311.
On the other hand, in the case of forming the discharge port 313, the end mill ML1 is set obliquely to the cylinder 311, in this case, in an inclining direction of the discharge port 313, and extruded in the inclining direction of the discharge port 313 as indicated by an arrow in FIG. 32, thereby forming a notch inclined with respect to the cylinder 311.
Since the suction port 312 and the discharge port 313 were formed in the cylinder 311 in the conventional case as described above, an edge (right upper edge in FIG. 31) of a suction passage side of the suction port 312 was made linear, and an air flow of sucked gas on the connecting portion with the suction passage was disturbed, increasing passage resistance. In addition, since the end mill ML1 had to be set obliquely to the cylinder 311, processing was necessary separately from drilling similar to that for other screw holes or lightening holes, consequently increasing the number of processing steps, and production costs.
In the refrigerant circuit using the two-stage compression rotary compressor of the internal intermediate pressure type, a frost deposit is grown in the evaporator, and thus defrosting must be carried out. However, if a high-temperature refrigerant discharged from the second rotary compression element for defrosting in the evaporator is supplied to the evaporator without being pressure-reduced by a pressure reducing device (including a case of direct supplying to the evaporator, and a case of supplying with only passage through the pressure reducing device but without being pressure-reduced), suction pressure of the first rotary compression element is increased, thereby increasing discharge pressure (intermediate pressure) of the first rotary compression element.
This refrigerant is discharged through the second rotary compression element. However, because of no pressure reductions, discharge pressure of the second rotary compression element is set equal to the suction pressure of the first rotary compression element. Consequently, a reversal phenomenon occurred in pressure between the discharge (high pressure) and the suction (intermediate pressure) of the second rotary compression element in the conventional case.
Furthermore, in the rotary compressor of the internal intermediate multistage compression type, on the bottom portion, pressure (high pressure) in the cylinder of the second rotary compression element is set higher than pressure (intermediate pressure) in the hermetically sealed container as the oil reservoir. Consequently, it was extremely difficult to supply oil from the oil hole of the rotary shaft into the cylinder by using the pressure difference, and lubrication was carried out only by the oil blended in the sucked refrigerant, causing a shortage of oil supply.